Glycosylation is a common post-translational modification in mammalian cells; both normal human immunoglobulins and therapeutic monoclonal antibodies (mAbs) produced in Chinese hamster ovary (CHO) cells are glycoproteins. Both pharmacokinetic properties and effector functions of therapeutic mAbs can be affected by glycosylation. Terminal sugars such as fucose and galactose may affect antibody-dependent cellular cytoxicity (ADCC) and complement-dependent cytoxicity (CDC; Wright, A. and S. L. Morrison, Trends Biotechnol (1997) 15:26-32). High mannose glycans may increase serum clearance of certain mAbs, thus potentially affecting efficacy (Goetze, et al., (2011) Glycobiology 21:949-59). Alternatively, high mannose glycoforms can increase the affinity of antibodies for Fc gamma III receptor, thus increasing ADCC activity of certain antibodies (Yu, et al. (2012) MAbs 4:475-87). Thus for each recombinant mAb, a certain glycosylation profile that best supports the therapeutic potential of the mAb needs to be maintained.
Methods for manipulating high mannose glycoform content of a protein in cell culture include changes in media compositions, osmolality, pH, temperature, etc. (Yu, et al., supra, Pacis et al., supra, Chee Furng Wong et al. (2005) Biotechnol Bioeng 89:164-177; Ahn, et al. (2008) Biotechnol Bioeng 101:1234-44). The effectiveness of these methods is specific to cell lines, molecule types and media environment and is typically obtained by trial and error. Additionally, these methods tend to also alter antibody productivity, cell culture behavior and other antibody quality attributes.
There still exists a need to identify a mechanism which can regulate high mannose glycoforms (particularly Mannose 5), on mAbs without compromising CHO production culture performance and antibody yield. Such a method would benefit the process development of therapeutic proteins. The invention provides a method that regulates high mannose glycoform content by manipulating levels of expression of proteins involved in the N-glycosylation pathway.